It is well known that rope pulley systems are useful in providing a mechanical advantage for lifting or lowering a load, the magnitude of the mechanical advantage typically being a function of the number and/or diametric size of each pulley wheel so that relatively heavy loads can be lifted or lowered by a single person pulling or releasing by hand the pulley rope. Thus, a typical rescue pulley system can easily support the weight of an accident victim and the rescuer during the rescue operation, often with a mechanical advantage in terms of force applied to or released from the pulley rope of 5 or 6 to one.
Many pulley rescue systems are known which are particularly suitable for so called self-rescuing, such as is described in DE202013003344, although they are not usually suitable for e.g. accident victims who are unconscious or otherwise disabled. In such circumstances the pulley system has to cope with the combined weight of the rescuer and accident victim, who may be secured by a harness to a stretcher, leaving the rescuer with the task of single-handedly raising or lowering the victim from a secure position up to the fully extended limit of the pulley system, and thereafter repositioning the pulley system for the next phase of the rescue. This requires the rescuer to pull on the free end of the pulley rope in order to raise or lower the entire load carried by the pulley system, and then to reposition anchors such as ‘rope grabs’ sufficiently securely for the next phase of safely raising or lowering the combined load. In order to do this, the pulley system must be restrained from running in the opposite direction required of the rescuer, this usually being achieved by means of a one-way brake system permitting the pulley rope to travel in one direction only during the lifting stage of the rescue whilst permitting controlled decent of the combined load being carried by the pulley system, as required. Such rope braking and rope releasing mechanisms can be complicated to operate by the rescuer, more particularly when in extreme circumstances, such as in confined spaces or within complex steel structures.
The present invention is derived from the realisation that there is a need for a simpler system of engaging or disengaging, as the case may be, the pulley rope brake from the pulley system.